1. Field of the Invention
The present invention relates to a phosphor having a host crystal having the same crystal structure as that of a CaAlSiN3 crystal phase that emits red light by absorbing light from a light emitting element such as LED, a method for producing the same, and an application of the same. More specifically, the present invention relates to a phosphor having a more improved emission efficiency than ever before, and a light emitting device with high brightness and long life by using the phosphor.
2. Description of the Related Art
A white LED is a device that emits white light in combination of a semiconductor light emitting element and a phosphor, and the combination of a blue LED and a YAG yellow phosphor is known as a typical example. However, since a YAG phosphor has an insufficient amount of red emission component, disadvantageously color rendering properties are insufficient for use in lighting, causing poor color reproducibility for an image display device such as a liquid crystal display backlight. Accordingly, in order to compensate for the red component of a white LED, a combination use of a nitride-based phosphor that emits red light with a YAG phosphor has been proposed (Patent Document 1).
It is known that, as a nitride-based phosphor that emits orange or red light, a CaAlSiN3-based nitride or oxynitride material having a host crystal of inorganic compound having the same crystal structure as that of a CaAlSiN3 crystal phase with an emission center of optically active element, Eu in particular, emits orange or red light with particularly high brightness (Patent Document 2).
Further improvement in emission characteristics of a phosphor is, however, still required to obtain a light emitting device with high brightness.